Method of electrodeposition of zinc



Patented Mar. 29, 1932 ,umranzys'rn UBLYN o.- rmron. communes-nae.rnansvm, son'm AFRICA METHOD OF ELEGTRODEPOSITION 01 ZINC Ho pavin Thisinvention relates to an improved -method of electrodeposition of zincand has 5 ri tyand high for its purpose of a new type,

of pure lead and to add to the solution a a greater or ter of thedeposit.

lue to improve the charac- The zinc metal so ob tained,'however, isalways contaminated to less degree with lead derived small amount offrom the anode and the deposited metal is but having brittle andrelatively difficult to work mechanically. According to the presentinvention, I employ an anode consisting mainly of lead alloyed with it acertain propor- 29 tion of a metal or metals standing belowlead in theelectro-chemical scale, such as silver, arsenic, bismuth, etc. I furtheradd to the solution a small proportion of an inorganic colloid such assilicic acid. It is frequently desirable to couple with the inorganiccolloid the addition of an organic colloid not as gum -arabicprecipitated by zinc sulphate solution, such or agar jelly. Under theseconditions the zinc deposit obtained is much purer than by the ordinarymethod and at the same time the deposits are of exceptionally goodquality, being very smooth, malleable, and ductile. It has been foundpossible to produce, directly from the cathode deposits, zinc foil-onlyone-sixteen thousandthsof an inch in thickness, and the metal may berolled out indefinitely without annealing.

In carryingthis invention into ploy an anode "consisting mainly of leadbut containing a small percentage, say 1%, of silver, bismuth, orarsenic. Other metals or combinations of metals electro-negative 'tolead may be employed although my preference is for. those mentioned, inthe order named. To the electrolyte I add a solution of silicic acidorsodium silicate in the proportion of about one to five pounds ofsoluble silica per ton of zinc deposited. To insure a smooth deposit,and more especiallyif impurities are likely to effect, I embe present inthe Application filed August 27, 1928. Serial No. 302,444.

electrolyte, the addition of a similar quantity of gum arabic, or of onequarter the amount of agar, is beneficial. The electrolysls ispreferably conducted under conditions descrlbed in prior patents of thepresent applicant, namely, in, the presence of a large proportion ofacid and at a high current density. Other conditions of electrolysismay, however, be employed.

It will be found that the zinc deposited un-. so der the aboveconditions carries only about one-tenth as much lead as doeselectrolytic zinc made in the usual way. Moreover the deposited metal,both in the form. of cathode and after melting, is remarkably ductileand 6a malleable and may be put through severe mechanical operationssuch as drawin \spinrung, and stamping, to an extent to w ich it isimpossible to subject ordinary zinc with success. 3e

It will be found further, that under the above conditions the powerrequired for electrolysis is substantially reduced as compared withordinary practice, because not only is the current efiiciencyexceptionally high, but the terminal voltage is lower than when usingthe ordinary conditions.

The metal obtained is also of special value in the plating of thin zincdeposits on other metals as, for example, in the roduction of galvanizediron and steel. wing to the high purity of the metal, the resistance tocorrosion is greater and'the adhesion of the zinc to the underlyingmetal is much stronger than when made by the ordinary method.

Having thus described my invention, what I claim and desire to secure byLetters Patcut is:

1. In the ele'ctro-deposition of zinc, the method of producing zincdeposits of great purityv and ductility which consists in using an anodecomposed of an alloy of lead with a small proportion of a metalelectro-negative to lead, and carrying out the electrolysis in thepresence of silicic acid.

2. In the electro-deposition of zinc, the method of producing zincdeposits of great purity and ductility which consists in usin an anodecomposed of an alloy of lead an silver, and carrying out theelectrolysis in the presence of silicic acid.

3. In the electro-deposition of zinc, the method of producing zincdeposits of great purity and ductility which consists in using ananodecomposed of an alloy of lead with a small proportion of metalelectro-negative to lead andcarrying out the clectrolysis in thepresence of silicic acid and gum. arabic.

URLYN C, TAINTON.

